Is it worth soundproofing your car?

Effective interior soundproofing is one of the many advantages of premium luxury cars. In the case of cheaper vehicles, manufacturers often aim to reduce production costs, which unfortunately translates into a lack of special care for sound insulation. Adequate soundproofing has a key impact on the comfort of both driver and passengers, while at the same time guaranteeing excellent sound reception in the car audio system.

The lower the class of car, the worse the soundproofing, unfortunately. The manufacturer has to save on something. If a car is already soundproofed at the factory, it is in many cases with low-quality materials. Noise in the car interior is very tiring, especially on long journeys, which in turn affects driving safety.

Every new car must meet certain requirements regarding the maximum external noise level during technical tests. These regulations are set out in the Regulation of the Minister of Infrastructure of 31 December 2002 on the technical conditions of vehicles and the scope of their necessary equipment (Acting Section 2003 No. 32 item 262), as amended. According to these regulations, the maximum noise level outside the vehicle is:

Passenger car with petrol engine - 93 dB (A)

Diesel passenger car - 96 dB (A)

However, the most important thing is what happens inside the cabin.

But what are the noise levels in the cabins of today's passenger cars? Let's check the results of the measurements carried out by the Auto-Decibel-DB service.

Before going into the precise results, it is worth understanding that the measurement of noise levels is done on a logarithmic scale. In theory, a difference of 3 dB (decibels) between different car models may seem small. However, in reality, a difference of 3 dB means a twofold increase in the noise level inside the vehicle, and 6 dB means a fourfold increase.

What causes noise in the car?

Much depends on the driving speed. When driving around town at speeds up to 50 km/h, the vehicle engine is the main source of noise. When speeds between 50 and 120 km/h are reached, the tyres become the main source of noise, while above 120 km/h the noise is mainly generated by air resistance.

When it comes to tyres, economy tyres, especially multi-season tyres, tend to be noisier. However, it is possible to improve the acoustic comfort of the vehicle by using premium tyres, which significantly reduce noise levels.

Modern engines are becoming quieter, but it is important to remember that as the vehicle ages and mileage increases, the engine can become noisier. This is the result of three main factors: increasing backlash, wear and tear on the mechanisms and lack of proper servicing.

Excessive noise reaching the interior of the car can also be the result of damaged door seals. Damaged seals increase the noise generated by air resistance. In addition, when driving in the city, ambient sounds that we do not necessarily want to hear can enter the vehicle, such as the loud sound of the engines of other vehicles, especially heavily tuned or worn-out ones, as well as the engine noise of motorbikes, especially sports bikes, and music from other cars.

According to various studies, busy urban streets can generate noise levels as high as 90 dB, and heavy vehicles and buses can exceed 95 dB. However, it is worth remembering that the safe noise level for humans is a maximum of 85 dB.

Why soundproof the interior of your car?

The soundproofing of a car's cabin is key to increasing driver and passenger comfort in a variety of situations. Whether for short journeys around town, where we are particularly exposed to external noise, or when driving at higher speeds on routes and motorways, where the main source of noise becomes air rush, tyres and other car components, sound reduction is essential. Less noise translates into less stress and irritation, which contributes to an overall more comfortable journey.

A soundproofed car cabin is also beneficial for the children being transported in the car, as it allows them to have a quieter journey. Furthermore, it is important for audiophiles, as even the best audio system will not give its full potential in a poorly soundproofed car. In addition, in a well soundproofed cabin you can freely make phone calls using hands-free kits, which is appreciated by business people.

Professional soundproofing aims to reduce the noise generated by the engine in the cabin. This can be achieved by soundproofing the partition between the passenger compartment and the engine, as well as by installing new soundproofing materials in the lower part of the bonnet. In addition, noises resulting from air noise are eliminated. To this end, new soundproofing elements are installed in the doors, the rear part of the vehicle and the boot lid, especially as the rear of the car is poorly soundproofed from the factory.

To reduce tyre noise, the vehicle floor and wheel arches are also subjected to a soundproofing process. In addition, it is necessary to eliminate resonances of the dashboard and its components that may be generated by the engine. Noises and creaks resulting from poorly fitted interior and boot components must also be eliminated.

It is worth noting that actual professional soundproofing of the vehicle interior can reduce noise levels by up to 4 dB. Noise measurement is carried out on a logarithmic scale, which means that a reduction of 3-4 dB represents a significant reduction in noise levels, even if this does not appear to be a significant value.

However, it is important to remember that the soundproofing process can increase the weight of the car, depending on the materials used. Using the best materials can increase the weight by a minimum of 20-30 kg, while inappropriate, cheap soundproofing materials can result in an increase of up to 90 kg. This, of course, affects fuel consumption.

It is worth noting that it is not always necessary to soundproof the entire car. In the case of vehicles with quiet engines, where the main source of noise is the tyres and exhaust system, the main focus can be on soundproofing the floor. In cars where the noise is mainly generated by the momentum of the air, it is important to check the condition of the seals, as well as the soundproofing of the doors and roof of the vehicle. In the case of cars with noisier engines, such as small city cars with diesel engines or small-litre engines with downsizing principles, it is sufficient to adequately soundproof the partition between the cabin and the engine compartment.

What are the best materials to soundproof a car?

The combination of butyl mats and rubber (rubber) foams is an effective and economical option for sound insulation and air tightness. A square metre of 2 mm thick butyl matting costs on average around £60, while the price for a square metre of rubber foam with adhesive is around £50. Both materials are characterised by their flexibility, water resistance, airtightness and relatively low weight.

Butyl matting consists of a layer of aluminium and a layer of rubber, which makes it extremely thin. Its installation is simple as it does not need to be heated. Many manufacturers supply butyl mats with an adhesive layer, which makes application even easier.

Rubber foams, used as an absorption layer, also exhibit moisture resistance and are excellent at dampening noise and resonance. This makes them an excellent complement to butyl mats, helping to increase the effectiveness of sound insulation.

The combination of these two flexible and robust materials is a sensible choice for those looking for an effective sound insulation and airtightness solution, while keeping costs relatively low.

Is it worth soundproofing a car on your own?

Soundproofing a car yourself is theoretically possible, but you should be aware that it is an extremely labour-intensive and complicated task, as you can see from the example above. It is worth bearing in mind that such a process may end in failure. Even if damage to plastic or upholstery components is avoided, there is a risk of unwanted vibrations or sounds. All it takes is one small mistake during the installation of the soundproofing elements, for example, which becomes a source of additional noise or interferes with the loudspeakers.

Particularly problematic for amateurs is soundproofing the bulkhead between the engine compartment and the cabin of the car. Here, too, unnecessary noise can occur, and many amateurs choose to dismantle the entire car dashboard, which is very complicated and can lead to problems.

It is also worth knowing that, in the case of new cars, soundproofing by yourself may result in the loss of the warranty. However, under the GVO (Guarantees of Vehiculum Omnium) laws, companies or workshops with the necessary authorisation can legally remove the upholstery and soundproof the cars, without risking the loss of the warranty.

For this reason, it is worth considering entrusting the car soundproofing process to professionals who have the knowledge and experience. Such specialists will use the right amount of insulation materials, install them in the right way, will not damage the car's interior elements and will perform the whole service quickly and efficiently. This ensures that the soundproofing process is carried out with the utmost care and produces the desired results.